Influence of inclined unconfined circular air jet impingement on local heat transfer characteristics of smooth flat plate

Abstract

The influence of inclined unconfined circular air jet impingement on local heat transfer characteristics of smooth flat plate is studied experimentally. The experimental investigation was conducted with jet inclination angles of 45°, 60° and 75°, jet Reynolds number of 12000–28000 and nozzle to target surface distance of 1–6. The Nu characteristics is studied in different radial direction angles on flat plate ranging from θ = 0° to 180° in stagnation and wall jet area for different z/d, Re and jet inclination configurations. The Nu characteristics are obtained by using an IR thermal imaging and thin foil approach. The Nu characteristics of different jet inclination angles (φ = 75°, 60° and 45°) was compared with vertical jet (φ = 90°) for different z/d and Re. Asymmetric in Nu characteristics increases with decrease in jet inclination about the geometric impingement point. With jet inclination, the maximum Nu value shifts away from geometric impinging point towards the uphill area of target plate. The displacement of maximum Nu from geometric impinging point towards the uphill area is highly pronounced at lower z/d and higher Re for a given jet inclination configuration. The isothermal Nu ring is reported at r/d ∼2 from geometric point in wall jet area. Within isothermal ring, Nu increases with radial direction angles from 0° to 180° and reverse behavior is observed outside the isothermal Nu ring. Correlations of Nu are obtained at geometric point and maximum Nu point with maximum deviation of ±10 %. Moreover, correlation for average Nu is also presented with and accuracy of ±3.4 %.